A robust stellar initial mass function (IMF) is crucial in any studies related to star formation. However, the direct measurement of the stellar IMF is confined to the local universe, limited by the resolving power of telescopes. Recently, a new method for accessing the stellar IMF beyond the local universe has been developed. The observed detection rate of transient lensed stars -- individual, massive, thus luminous stars in strongly lensed galaxies that are temporarily detectable upon stellar microlensing -- can serve as a probe to break the IMF-star formation history degeneracy in studies utilizing spectral energy distribution fitting, hence providing a window to look at the IMF at a subsample of gravitationally lensed galaxies. In this proceeding, I summarize the contributed talk given at IAUS402 entitled the same as this contribution and highlight some key results, which currently show no evidence for a top-heavy IMF in $z \approx 1$ galaxies.
In the current paper we consider the prospects of observation of gravitationally lensed sources in far-infrared and submillimeter wavelength ranges by the future space telescopes equipped with actively cooled main mirrors. We consider the possibility of solving some of the important cosmological and astrophysical scientific tasks by observation of gravitationally lensed sources. The number counts of lensed sources for wavelengths from 70$μm$ up to 2000$μm$ were calculated. We discuss the distribution of lensed sources at different redshifts and magnification coefficients and also mass distribu…
A Targeted Search for Variable Gravitationally Lensed Quasars
University of California, Los Angeles（加州大学洛杉矶分校）；Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）；University of San Francisco（旧金山大学）；Gemini Observatory / NSF’s NOIRLab（Gemini 天文台/美国国家科学基金会NOIRLab）；Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo（东京大学 Kavli宇宙物理与数学研究所）；Carnegie Mellon University（卡内基梅隆大学）；University of Hawaii（夏威夷大学）
We present an analysis of archival observations with the Atacama Large (sub-)Millimetre Array (ALMA) of the gravitationally lensed quasar MG J0414+0534, which show four compact images of the quasar and an Einstein ring from the dust associated with the quasar host galaxy. We confirm that the flux-ratio anomalies observed in the mid-infrared and radio persists into the sub-mm for the continuum images of the quasar. We report the detection of CO (11-10) spectral line emission, which traces a region of compact gas around the quasar nucleus. This line emission also shows evidence of a flux-ratio a…
We present an analysis of seven strongly gravitationally lensed quasars and the corresponding constraints on the properties of dark matter. Our results are derived by modelling the lensed image positions and flux-ratios using a combination of smooth macro models and a population of low-mass haloes within the mass range 10^6 to 10^9 Msun. Our lens models explicitly include higher-order complexity in the form of stellar discs and luminous satellites, as well as low-mass haloes located along the observed lines of sight for the first time. Assuming a Cold Dark Matter (CDM) cosmology, we infer an a…
Follow-up observations of (sub-)mm-selected gravitationally-lensed systems have allowed a more detailed study of the dust-enshrouded phase of star-formation up to very early cosmic times. Here, the case of the gravitationally lensed merger in HATLAS J142935.3-002836 (also known as H1429-0028; z_lens=0.218, z_bkg=1.027) is revisited following recent developments in the literature and new APEX observations targeting two carbon monoxide (CO) rotational transitions J_up=3 and 6. We show that the line-profiles comprise three distinct velocity components, where the fainter high-velocity one is less …
Cross-referencing a watchlist of galaxy groups and clusters with transient detections from real-time streams of wide-field survey data is a promising method for discovering gravitationally lensed explosive transients including supernovae, kilonovae, gravitational waves and gamma-ray bursts in the next ten years. However, currently there exists no catalogue of objects with both sufficient angular extent and depth to adequately perform such a search. In this study, we develop a cluster-finding method capable of creating an all-sky list of galaxy group- and cluster-scale objects out to $z\simeq1$…
SDSS J133401.39+331534.3: A New Subarcsecond Gravitationally Lensed Quasar
z = 2.426的类星体SDSS J133401.39+331534.3是一个双像引力透镜类星体，像间距为0.833。该物体首先在斯隆数字巡天类星体透镜搜索中被确定为透镜类星体候选者，然后通过斯巴鲁和夏威夷大学2.2米望远镜的后续观测确认为透镜系统。根据类星体光谱中的吸收线以及星系的颜色，我们估计透镜星系的红移为0.557。特别是，我们观察了斯巴鲁望远镜AO188自适应光学与激光导星，以获得准确的天体测量，这很好地证明了有用的激光导星自适应光学成像研究强透镜系统。我们的质量模型与改进的天体测量意味着附近的明亮星系$\sim 4"$除了透镜星系很可能会影响透镜的潜力。
We present a spatio-temporal AI framework that concurrently exploits both the spatial and time-variable features of gravitationally lensed supernovae in optical images to ultimately aid in future discoveries of such exotic transients in wide-field surveys. Our spatio-temporal engine is designed using recurrent convolutional layers, while drawing from recent advances in variational inference to quantify approximate Bayesian uncertainties via a confidence score. Using simulated Young Supernova Experiment (YSE) images of lensed and non-lensed supernovae as a showcase, we find that the use of time…
The CASSOWARY spectroscopy survey: A new sample of gravitationally lensed galaxies in SDSS
明亮的引力透镜星系为我们提供了高红移星系的最详细的图像。然而，由于极少数的超亮z~2透镜系统已证实的红移，大多数详细的光谱研究已被限制在他们的范围。为了增加可用于详细跟踪的明亮透镜星系的数量，我们在斯隆数字巡天（SDSS）中开展了一项光谱活动，目标是宽分离（>3角秒）星系-星系透镜候选者。在我们CASSOWARY调查的早期努力的基础上，我们针对SDSS中的候选星系-星系透镜系统的大样本，使用完善的搜索算法识别位于明亮的红色星系周围的蓝色弧状结构。在本文中，我们提出了一个新的红移目录包含25个透镜源SDSS通过光谱的候选星系星系透镜系统的后续确认。在这个新的样本中包括两个已知的z~2最亮的星系（r=19.6和19.7），一个z=1.43的低金属丰度（12 + log（O/H）~8.0）的极端星云线发射星系，以及许多可能进行详细跟踪的系统。源红移跨度为0.9<z<2.5（中位红移为1.9），它们的光学星等范围为19.6<r <22.3. We present a brief source-by-source discussion of the spectroscopic properties extracted from our confirmatory spectra and discuss some initial science results. With mo…
We present a machine learning method for the reconstruction of the undistorted images of background sources in strongly lensed systems. This method treats the source as a pixelated image and utilizes the Recurrent Inference Machine (RIM) to iteratively reconstruct the background source given a lens model. Our architecture learns to minimize the likelihood of the model parameters (source pixels) given the data using the physical forward model (ray tracing simulations) while implicitly learning the prior of the source structure from the training data. This results in better performance compared …
The Chandra observations of several gravitationally lensed quasars show evidence for flux and spectral variability of the X-ray emission that is uncorrelated between images and is thought to result from the microlensing by stars in the lensing galaxy. We report here on the most detailed modeling of such systems to date, including simulations of the emission of the Fe K-alpha fluorescent radiation from the accretion disk with a general relativistic ray tracing code, the use of realistic microlensing magnification maps derived from inverse ray shooting calculations, and the simulation of the lin…
Recently, there have been two landmark discoveries of gravitationally lensed supernovae: the first multiply-imaged SN, "Refsdal", and the first Type Ia SN resolved into multiple images, SN iPTF16geu. Fitting the multiple light curves of such objects can deliver measurements of the lensing time delays, which are the difference in arrival times for the separate images. These measurements provide precise tests of lens models or constraints on the Hubble constant and other cosmological parameters that are independent of the local distance ladder. Over the next decade, accurate time delay measureme…
When the light from a distant object passes very near to a foreground galaxy or cluster, gravitational lensing can cause it to appear as multiple images on the sky. If the source is variable, it can be used to constrain the cosmic expansion rate and dark energy models. Achieving these cosmological goals requires many lensed transients with precise time delay measurements. Lensed supernovae (SN) are attractive for this purpose because they have relatively simple photometric behavior, with well-understood light curve shapes and colours $-$ in contrast to the stochastic variation of quasars. Here…
Detectability of Gravitationally Lensed Kilonovae in the Rubin LSST
Inter-University Centre for Astronomy and Astrophysics（天文与天体物理大学间中心）；Kavli Institute for the Physics and Mathematics of the Universe (IPMU)（宇宙物理与数学卡弗里研究所）
High-precision cosmological probes have revealed a small but significant tension between the parameters measured with different techniques, among which there is one based on time delays in gravitational lenses. We discuss a new way of using time delays for cosmology, taking advantage of the extreme precision expected for lensed fast radio bursts (FRBs), which are short flashes of radio emission originating at cosmological distances. With coherent methods, the achievable precision is sufficient for measuring how time delays change over the months and years, which can also be interpreted as diff…
Due to the expansion of our Universe, the redshift of distant objects changes with time. Although the amplitude of this redshift drift is small, it will be measurable with a decade-long campaigns on the next generation of telescopes. Here we present an alternative view of the redshift drift which captures the expansion of the universe in single epoch observations of the multiple images of gravitationally lensed sources. Considering a sufficiently massive lens, with an associated time delay of order decades, simultaneous photons arriving at a detector would have been emitted decades earlier in …
COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses VIII. Deconvolution of high resolution near-IR images and simple mass models for 7 gravitationally lensed quasars
Strongly lensed supernovae can be detected as multiply imaged or highly magnified transients. In order to compare the performances of these two observational strategies, we calculate expected discovery rates as a function of survey depth in five grizy filters and for different classes of supernovae (Ia, IIP, IIL, Ibc and IIn). We find that detections via magnification is the only effective strategy for relatively shallow pre-LSST surveys. For survey depths about the LSST capacity, both strategies yield comparable numbers of lensed supernovae. Supernova samples from the two methods are to a lar…
Secure confirmation that a gravitational wave (GW) has been gravitationally lensed would bring together these two pillars of General Relativity for the first time. This breakthrough is challenging for many reasons, including: GW sky localization uncertainties dwarf the angular scale of gravitational lensing, the mass and structure of gravitational lenses is diverse, the mass function of stellar remnant compact objects is not yet well constrained, and GW detectors do not operate continuously. We introduce a new approach that is agnostic to the mass and structure of the lenses, compare the effic…
We identify a binary black hole (BBH) merger that appears to be multiply lensed by an intervening galaxy. The LIGO/Virgo events GW170809 and GW170814 have indistinguishable waveforms separated by 5 days, and overlap on the sky within the 90\% credible region. Their strain amplitudes are also similar, implying a modest relative magnification ratio, as expected for a pair of lensed gravitational waves. The phase of the two events is also consistent with being the same, adding more evidence in support of both events originating from the same BBH merger. The difference in the published inferred di…
An archival search for gamma-ray bursts gravitationally lensed by galaxy clusters
Institute of Cosmology and Gravitation, University of Portsmouth（宇宙学与引力研究所，朴茨茅斯大学）；School of Physics and Astronomy, University of Birmingham（物理与天文学学院，伯明翰大学）；Institute for Gravitational Wave Astronomy, University of Birmingham（引力波天文学研究所，伯明翰大学）；Department of Astrophysics, University of Vienna（天体物理学系，维也纳大学）
